1. Field of the Invention
The present invention relates to the manufacture of fully drawn continuous multifilament nylon yarns and to a spinning machine used for the manufacture of these yarns and more particularly to a conversion process used to provide such a yarn spinning machine.
2. Description of Related Art
Makers of continuous multifilament nylon yarns sell their product into apparel manufacturing markets where a mix of textured and untextured yarn is consumed. Untextured yarns are also called flat or fully drawn yarn.
Typically, textured yarn is prepared from a feed yarn, a partially oriented yarn (POY), by draw-twisting and heat setting. Fully drawn or fully oriented yarn (FOY), is prepared by further drawing POY in a split process. Alternatively, FOY is directly spun in a coupled process of spinning and drawing. The terms POY and FOY generally distinguish nylon yarns having an elongation to break of  greater than 60% and  less than 60% respectively; see xe2x80x9cLOY MOY POY HOY FOYxe2x80x9d by H. Treptow, Man-Made Fiber Year Book (CTI) 1986, page 6.
Well-known processes and apparatus to melt spin nylon multifilament POY at high spin speeds are described by Chamberlin et al. in U.S. Pat. No. 4,646,514. However, various spinning machine configurations for POY are employed throughout the industry. These POY machine configurations may be xe2x80x9cgodetlessxe2x80x9d, a most compact apparatus, where the yarn is wound without passing over roll surfaces or with godets. In such a POY machine with godets the yarn passes over multiple roll surfaces prior to wind-up; see Chemical Fibers International (CFI) Vol. 46, January 1996, pages 37-40.
Flat yarn or FOY spinning machine configurations are disclosed by McNamara et al. in U.S. Pat. No. 4,123,492; and by Kemp et al. in Swiss Patent No. CH-623 611. Generally, the FOY process apparatus requires some means to draw or stretch the yarn. A differential roll speed between a feed roll onto which the yarn is wrapped several times and a draw roll, also where multiple yarn wraps occur, serve to effect the stretch or draw. Some means to relax the fully drawn nylon yarn to allow good yarn package build in winding is necessary for high productivity. This yarn relax means may include a steam box as taught in Kemp at al. or a heated roll assembly.
The makers of multifilament nylon yarns usually prepare both POY and FOY for various end uses. The spinning machine asset investment by each maker usually reflects the relative fraction of POY to FOY consumed by the apparel market into which the maker sells product. However, market demands shift over time as fashion trends may dictate a changing requirement for POY versus FOY consumed in the market. As a result, a fixed machine asset may present certain liabilities. While recognized as a long standing dilemma to the makers of POY and FOY nylon yarns, the ability to shift a POY spinning machine asset to a FOY spinning asset has not been addressed in the literature.
The present invention deals with this situation where a maker of nylon multifilament yarns must respond to a drop in the demand for textured apparel yarns (POY) and a corresponding growing requirement for fully drawn yarn (FOY) consumed in the market.
We have found an effective and economical method to convert a POY machine to spin FOY yarns resulting in a novel apparatus for making fully drawn yarn. This conversion process of our invention is reversible and may allow spinning assets to xe2x80x9cswingxe2x80x9d between product types in response to-market demands.
A prior art godetless POY machine is shown in FIG. 1. Such a prior art machine is readily converted to a FOY machine via the process of our invention. Our incentive to make this conversion resulted largely from space restrictions, both vertical and horizontal, imposed by traditional POY machine design. We have found productivity and investment criteria impose stringent design standards on facilities of POY machines. Often the yarn winding assemblies are less than 300 mm apart (on average). Introducing a typical prior art feed and draw roll assembly to the midsection of closely spaced POY machines would result in undue complexity and be expensive. Moving the winder assemblies farther apart to accommodate prior art feed and draw roll mechanisms and a yarn relax means is not a simple and economical option and would inhibit a readily reversible conversion of machines.
Where incentive exists to shift POY spinning assets to FOY spinning assets without substantive modification of winding assemblies, there is a need for a simple, inexpensive, and compact yarn drawing and yarn relaxing assembly to meet the space restriction and investment limitations imposed by an existing POY spinning facility.
The present invention, i.e., a conversion method and an apparatus, and other objects of the invention will be clear from the following description.
The invention relates to a fully oriented yarn spinning machine for making a first and second plurality of fully oriented multifilament yarns, comprising: at least a first spinning assembly having a spin pack containing a spinneret plate for providing a plurality of filaments; a quench chimney for receiving and cooling the filaments; a finish applicator and convergence guide for receiving the filaments from the spinneret plate, for applying finish to the filaments, and for converging the filaments into a first and a second plurality of multifilament yarns; a first and a second alignment guide for receiving the first and second plurality of the multifilament yarns from the finish applicator and convergence guide; a first and a second stepped roll assembly for receiving the first and the second plurality of the multifilament yarns from the first and the second alignment guides, respectively, and for drawing the multifilament yarns to increase their length by a fixed amount; a steam relax unit between the first and the second unheated rotatable stepped feed and draw roll assemblies, the steam relax unit for receiving the multifilament yarns from the unheated rotatable stepped feed and draw roll assemblies and for applying steam to the multifilament yarns to stabilize the multifilament yarns; a first and a second pre wind-up guide for maintaining the separation of the multifilament yarns; and a first and a second windup assembly for winding the first and the second plurality of the multifilament yarns into a first and a second plurality of packages.
The fully oriented yarn spinning machine may optionally have an exit guide for maintaining the separation of the multifilament yarns within the steam relax unit and for directing the first and second plurality of the multifilament yarns.
The invention further relates to a yarn spinning machine conversion process for converting a partially oriented yarn spinning machine to a fully oriented yarn spinning machine, the partially oriented yarn spinning machine having a first spinning assembly in a confined space between adjacent spinning assemblies, the process comprising: relocating and/or replacing a first and a second alignment guide for receiving a first and a second plurality of multifilament yarns; mounting in the confined space a first and a second unheated rotatable stepped feed and draw roll assembly for receiving the first and the second plurality of the multifilament yarns from the first and the second alignment guides, respectively, and for drawing the multifilament yarns to increase their length by a fixed amount; installing in the confined space a steam relax unit between the first and the second unheated rotatable stepped feed and draw roll assemblies, the steam relax unit for receiving the multifilament yarns from the unheated rotatable stepped feed and draw roll assemblies and for applying steam to the multifilament yarns to stabilize the multifilament yarns before they are directed to a first and a second windup assembly, respectively, for winding the first and the second plurality of the multifilament yarns into a first and a second plurality of packages.
Optionally the conversion process includes adding an exit guide for maintaining the separation of the multifilament yarns within the steam relax unit.